In StringDB you can analyse species and export the interaction data respectively, and plot the interactions figure with different colours or shapes in Cytoscape.

In otherwise, you can try Dapple, http://www.broadinstitute.org/mpg/dapple/dappleTMP.php#DAPPLE stands for Disease Association Protein-Protein Link Evaluator. DAPPLE looks for significant physical connectivity among proteins encoded for by genes in loci associated to disease according to protein-protein interactions reported in the literature. The hypothesis behind DAPPLE is that causal genetic variation affects a limited set of underlying mechanisms that are detectable by protein-protein interactions. Please refer to the DAPPLE publication for full details.